Current ice melt rate in Pine Island Glacier may go on for decades
A study of the Pine Island Glacier could provide insight into the patterns and duration of glacial melt.
The Pine Island Glacier, a major outlet of the West Antarctic Ice Sheet, has been undergoing rapid melting and retreating for the past two decades. But new research by an international team including researchers from Lawrence Livermore National Laboratory shows that this same glacier also experienced rapid thinning about 8,000 years ago.
Using LLNL’s Center for Accelerator Mass Spectrometry to measure beryllium-10 produced by cosmic rays in glacially transported rocks, Lawrence Livermore researchers Bob Finkel and Dylan Rood reported that the melting 8,000 years ago was sustained for decades to centuries at an average rate of more than 100 centimeters per year. This is comparable to modern-day melting rates.
The findings indicate that modern-day melting and thinning could last for several more decades or even centuries. The research appears in the Feb. 20 issue of Science Express.
“Pine Island Glacier has experienced rapid thinning at least once in the past. Once set in motion, rapid ice sheet changes in this region can persist for centuries,” said Finkel, one of the authors of the new findings.
Ice mass loss from the Pine Island-Thwaites sector dramatically contributes to the sea level of the West Antarctic Ice Sheet. The Pine Island Glacier is currently experiencing significant acceleration, thinning and retreat. The rate of thinning from 2002-2007 on the grounding line (the part where the glaciers export the ice down the continent and lose contact to the ground and become a floating ice shelf) was between 1.2 meters per year and 6 meters per year.
The change is likely tied to the increased influx of warm water to the cavity under the ice shelf at the glacial front.
Dramatic changes over longer timescales — from centuries to millennia — are somewhat limited, so there is considerable uncertainty associated with model projections of the future evolution of timing and ice loss of the Pine Island Glacier. Current geological research is tied to the grounding line retreat across the continental shelf. However, little is known about the terrestrial thinning history and how the ice stream evolved from 8,000 years ago to the onset of present-day thinning.
The team found that there was a direct correlation from glacial-geological samples consisting of cobblestones and granite boulders from the Hudson Mountains to rapid thinning in the Pine Island Glacier system about 8,000 years ago.
“The melting of the Pine Island Glacier at a rate comparable to that over the past two decades is rare but not unprecedented,” Rood said. “Ongoing ocean-driven melting of the glacial ice shelf in current times may result in continued rapid thinning and ground line retreat for several more decades or even centuries.”
Other institutions involved in the research include: The British Antarctic Survey; Durham University; University of California, Berkeley; University of California, Santa Barbara; Alfred Wegener Institute Helmholtz-Centre for Polar and Marine Research; Berkeley Geochronology Center; Lamont-Doherty Earth Observatory; and Columbia University.
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I thought Antarctic glaciers were expanding?
It has all happened before.
This weekend there was a fascinating programme on BBC(4) about the Inca Tiwanaku civilisation that dominated the region of lake Titicaca, 12,000 feet up in the Andes. It evolved an advanced communial agricultural economy, fed by Andean melt waters, that thrived for the better part of the first millenium AD, with astounding monumental architecture. It disappeared at the end of the first millenium because of declining precipitation in the mountains, over a period of some four centuries.
NATURAL Catastrophic Climate Change,
Yet another overhyped press release about a scientific paper. The paper itself appears to be solid bread and butter research on the history of the Pine Island glacier. But of course that isn’t exciting enough for the press release which tries very hard to link it all to climate catastrophe and dire predictions for the future. It is very “dramatic”.
Dramatically! Wow! But since the sea level changes at pretty much the same rate around the West Antarctic Ice Sheet as it does in other places, this is very puzzling. Something isn’t quite right here. A little less attention paid to drama and a little more paid to accuracy and precision might have helped.
Wasn’t the sea level like 300 ft lower at that time?
The sea floor must be being scoured away by this glacier as it pushes out to sea. So the sea floor could be lowered over time and then the glacier floats and breaks away at a line further in. Then new deposits build up and the sea floor comes up again?
Just thinking..
@Lou: 7000 years ago it was only around 4 metres lower than present while 8000 years ago it was 15 metres lower. The last time it was 100 metres lower looks to have been about 14000 years ago near the end of the last ice age. I hope I’ve got those figures about right.
hmm, you take 6 months of satellite data in 2006 and compare it with two completely different land based sets from 20 and 40 years ago, and what do you get? rapid melting! 73% more since 1974!
http://www.ess.uci.edu/researchgrp/erignot/files/RignotGRL2008.pdf
8000 years ago? how about the last 20 years!
8000 years ago the coal fired power plant, the SUV, the wood burning stove and other modern industrial age accoutrements of the planet destroying human race were invented .
This first industrial revolution caused the Pine Island Glacier to begin melting – as the CONSENSUS has determined. But the folks at Lawrence Livermore make no mention of this at all!
I smell a rat here!!! Big bad oil is once again funding a bogus, self-servicing study.
LL researchers should be banned, prohibited from publishing any of their work or speaking at any
“Serious” climate conferences.
Further, any papers they have disseminated must be immediately collected and burned in one massive AGW-NACHT bonfire.
All together now AGW patrons, repeat after me: SIEG HEIL!! SIEG HEIL!! SEIG HEIL !!
Haven’t read the full paper, but the abstract represents a much less alarming situation (“show that this thinning was sustained for decades to centuries at an average rate of 100 cm-1, comparable to today’s thinning rates.”) than an earlier 2008 GSA paper ( http://epic.awi.de/16986/1/Joh2007b.pdf ) on the same subject by three of the same authors.
That paper stated: “Dramatic changes (acceleration, thinning, and grounding-line retreat of major ice streams” in the Amundsen Sea sector of the West Antarctica Ice Sheet (WAIS) have been observed in the past two decades, but millenial-scale context for these changes is not yet known. … Our data provide the first evidence that puts into context recent rates of thinning of the WAIS in the Amundsen Sea Embayment and demonstrates that these are unusually rapid.”
Seems that this 2014 paper provides more of the “millenial-scale context” and current thinning isn’t as bad as was thought previously. And since “This region is critically important because changes are happening faster here that anywhere else in the West Antarctica Ice Sheet (WAIS). In addition, this sector has long been identified as the “weak underbelly” of the WAIS (Huges, 1981), and has the potential to raise sea level by as much as ~1 m (Holt etal., 2006; Vaughan et al., 2006).”
For once, it isn’t as bad as we thought. The beginning of less alarmism as the “hiatus” persists? Let’s hope.
finishing my next to the last paragraph: “… (Vaughan et al., 2006).”, then it’s not as likely that present sea level rise from this area will be any more rapid that previously either.
I am not convinced that it is particularly reassuring that the Pine Island Glacier is now shrinking at a rate comparable to the major melt period at the end of the last glacial period when temperatures were climbing and sea level rose by around a foot per decade during the A1 meltwater pulse.
Why no mention of volcanic influence??
… Or is that an inconvenient truth..
http://www.livescience.com/2242-buried-volcano-discovered-antarctica.html
melting 8,000 years ago was sustained for decades to centuries at an average rate of more than 100 centimeters per year. This is comparable to modern-day melting rates.
The findings indicate that modern-day melting and thinning could last for several more decades or even centuries.
Of course it “could”, but isn’t this a non sequitur?
Why exactly should it do the same now as it did 8000 years ago?
(In the caption A massive crack rus about 29 kilometers presumably should be “runs”)
[Done. Thank you. Mod]
It would also be a non sequitur to see a similar rate in the past and assume that because it happened before naturally there is no human influence this time nor reason for concern.
The point really is that the bedrock geometry and ocean currents in this region make it more sensitive to changes, natural or otherwise. Given the amount of ice in the catchment, it is yet another good reason to be extremely cautious about the planetary scale experiment on the atmosphere and climate we are currently performing.
Leo Geiger says:
February 24, 2014 at 6:06 am
——————————————————
You forgot the /sarc tag
Don’t tell Mosher.
izen says:
February 24, 2014 at 5:37 am
Izen, could you break that long sentence-paragraph down into a number of subject/predicate pairs so that we can understand what you think that you do?
From the article:
Hmmmmn.
So, we get entertained by excited press releases and convoluted explanations from lots of professional CAGW-funded organizations when an existing Antarctic glacier thins by 1.2 meters a year, when an existing glacier gets a crack in it (but doesn’t thin or go anywhere but “might” go somewhere in a few years.
But ….
When the Antarctic sea ice is ABOVE its historical normal by 1.2 Million square kilometers – an area the size of Hudson Bay and right at half the size of Greenland itself … We hear nothing.
Yet, just last October, the Antarctic sea ice anomaly was not only “above average’ it was “above average” so much that it reflected more sunlight than half of Greenland, at the same average latitude as Hudson Bay.
And nobody said anything. To the CAGW religion, increasing sea ice by massive amounts didn’t support their agenda, so, it didn’t happen.
to measure beryllium-10 produced by cosmic rays in glacially transported rocks, [they] reported that the melting 8,000 years ago was sustained for decades to centuries at an average rate of more than 100 centimeters per year.
How’s that again? Glacially transported rocks get moved, and moved again, again and again. The age control on the dating is remarkable. Not to mention the implied precision on rates. Be-10 dating of the rocks require many assumptions about pre-exposure history. What is the cosmic ray attenuation per 100 m of ice? From where did the samples come?
There are many degrees of freedom to be accounted for.
The reality is these glaciers ground and then unground all the time. When they unground the flow will increase because of the buildup during the time it was grounded. All that is happening is the flow that was restricted now occurs. We know from measurements of the south polar atmosphere and the Southern Ocean that neither one is warming. Hence, there is nothing man made about these changes. It is either just normal variation or geological.
Greenland’s northern shore was getting pounded by waves generated in an ice-free Arctic Ocean at about the same time. Surprising, thus, that the Holocene Climatic Optimum doesn’t receive a mention. I hope I won’t upset anyone by thinking in this way.
@- Réaumur
“Why exactly should it do the same now as it did 8000 years ago?”
Because similar processes are in operation. Global warming.
Specifically the sea surface temperature is rising and that heat is getting into the deeper ocean currents which are now melting the underside of several Antarctic ice sheleves.
Last time, 8000 years ago, it was down to the timing of perhelion in the terrestrial year, now its the rise in CO2.
It has been shown that when doomsday prophecy fails as, will the CAGW prophecy, the irrefutable failure of a prophecy does not cause true believers (people who have committed themselves to a belief both emotionally and by their life choices) to reconsider. They, the zealots, become even more fervent, and proselytize even harder.
So, we see the political machine with likes of the U.N., Mr. Kerry, Mr. Gore and other thieves, using all the doomsday support money being poured into the collective research centers and colleges with the intent to sway the dumb-downed public with propaganda produced from of bad science.
The glaciers are going to come and go. Expand and retract. Proof that the weather changes with or without our help. Recall the notion to spread black soot on the north pole region to melt it…save the planet!
“The change is likely tied to the increased influx of warm water to the cavity under the ice shelf at the glacial front.”
WUWT? How can the glacier be “held back” or accelerated on the continent by the floating section, warm water or cold. Am I missing something here? Can someone explain?
Question:
Since Antarctica has much higher Ice accumulation that average and is very cold, why is there glacial retreat these days? One would think that the glacier would be at a stand still or growing?